1. Field
The present disclosure relates to a bobbin thread winder which is provided in a sewing machine arm to be drivingly coupled to a timing pulley driven by a sewing machine motor, thereby winding a thread supplied from a thread supply source on a bobbin, and a sewing machine equipped with the bobbin thread winder.
2. Related Art
Various types of sewing machines such as lock stitch sewing machines include an arm in which a rotary hook is provided. A bobbin on which a bobbin thread is wound is detachably attached to the rotary hook so that a bobbin thread is supplied thereto. When the bobbin thread has been consumed in a sewing operation, the bobbin is detached and a thread of thread spool is wound on the bobbin by a bobbin thread winder provided in an arm of the sewing machine.
For example, Japanese Patent Application Publication, JP-A-H09-313763, discloses a conventional bobbin thread winder which is drivingly coupled to a timing pulley driven by a sewing machine motor, thereby winding a thread supplied from a thread supply source on a bobbin. The above-noted publication corresponds to U.S. Pat. No. 5,816,512. More specifically, the disclosed bobbin thread winder includes a thread winding shaft protruding upward from an upper surface of the arm, a rubber ring provided on a lower end of the thread winding shaft, and a bobbin presser provided near the thread winding shaft.
In winding the bobbin thread, the bobbin which has been emptied is put onto the thread winding shaft, and the distal end of the thread drawn from a thread spool is wound onto the bobbin by a small amount. Thereafter, the thread winding shaft is moved to the bobbin presser side. A spring force of a torsion coil spring presses the rubber ring on the lower end of the thread winding shaft against a side of a timing pulley. When the operator then operates a start/stop switch, torque developed by a sewing machine motor rotates the rubber ring, the thread winding shaft and the bobbin together via a pulley, whereby the thread is wound on the bobbin.
When an amount of thread wound on the bobbin is increased with progress of the bobbin thread winding, an outer periphery of the wound thread is brought into contact with the bobbin presser. The rotation of the bobbin is continued even after contact of the wound thread with the bobbin presser. Accordingly, when an amount of wound thread is further increased, a relative pressing force is exerted on the thread winding shaft by the bobbin presser. As a result, the thread winding shaft is moved away from the bobbin presser against the spring force of the torsion coil spring. Consequently, a contact force between the rubber ring and the pulley is gradually reduced. When a predetermined amount of thread is finally wound on the bobbin, the rubber ring is moved to a location where the rubber ring departs from the side of the pulley. At last, a rotational force of the pulley is not transmitted to the rubber ring such that rotation of the thread winding shaft is stopped.
However, rotation is transmitted by a frictional force between the side of the pulley and the outer periphery of the rubber ring in the above-described conventional bobbin thread winder. Accordingly, since slippage between the side of the pulley and the outer periphery of the rubber ring results in attrition, partial wear of the rubber ring is increased with use for a long period. As a result, rotation of the rubber ring produces rumble and the winding shaft results in irregular rotation. Consequently, there is a possibility that the bobbin thread winding may be disrupted. In this case, a countermeasure such as replacement of the rubber ring needs to be taken.